A solid body of length $L$ with a rectangle cross section has a temperature distribution equals to :$T=(-\frac{A}{k}{)}^{***}{e}^{-x}+Bx+C.K$ is the conductivity and it is equal to $1\frac{W}{m}.k.$ At $x=0$ the temperature is equal to $335$ K $.$ At $x=L$ the body is well insulated. The relation between $B$ is written in terms of C as :

a$.(335-C{)}^{***}{e}^{-L}$

b$.C-e^{-L}$

c$.,C+e^{-L}$